Chin-Sean Sum

Beam codebook based beamforming protocol for multi-Gbps millimeter-wave WPAN systems

In order to realize high speed, long range, reliable transmission in millimeter-wave 60 GHz wireless personal area networks (60 GHz WPANs), we propose a beamforming (BF) protocol realized in media access control (MAC) layer on top of multiple physical layer (PHY) designs. The proposed BF protocol targets to minimize the BF set-up time and to mitigate the high path loss of 60 GHz WPAN systems. It consists of 3 stages, namely the device (DEV) to DEV linking, sector-level searching and beam-level searching. The division of the stages facilitates significant reduction in setup time as compared to BF protocols with exhaustive searching mechanisms. The proposed BF protocol employs discrete phase-shifters, which significantly simplifies the structure of DEVs as compared to the conventional BF with phase-and-amplitude adjustment, at the expense of a gain degradation of less than 1 dB. The proposed BF protocol is a complete design and PHY-independent, it is applicable to different antenna configurations. Simulation results show that the setup time of the proposed BF protocol is as small as 2% when compared to the exhaustive searching protocol. Furthermore, based on the codebooks with four phases per element, around 15.1 dB gain is achieved by using eight antenna elements at both transmitter and receiver, thereby enabling 1.6 Gbps-data-streaming over a range of three meters. Due to the flexibility in supporting multiple PHY layer designs, the proposed protocol has been adopted by the IEEE 802.15.3c as an optional functionality to realize Gbps communication systems.

IEEE 802.15.3c: the first IEEE wireless standard for data rates over 1 Gb/s

This article explains the important features of IEEE 802.15.3c, the first wireless standard from IEEE in the 60-GHz (millimeter wave) band and its development. The standard provides three PHY modes for specific market segments, with mandatory data rates exceeding 1 Gb/s. During the span of the standard development, new contributions to wireless communication technology were also made, including a new channel model, a codebook-based beamforming scheme, and a low-latency aggregation method.

Single carrier transmission for multi-gigabit 60-GHz WPAN systems

This paper proposes a new channel model for millimeter wave (60 GHz) for indoor applications, power amplifier and phase noise models at 60 GHz, an optimal global channelization over 9 GHz bandwidth, common mode signaling to bridge SC (single carrier) and OFDM (orthogonal frequency division multiplex) camps, and a robust payload as well as a header and preamble design for single carrier for practical applications. The computer simulations have validated these new proposals for WPAN (wireless personal are network) design and significantly contributed a lot to global (IEEE802.15.3c) standardization which will be closed in the near future by issuing system specifications.

Virtual time-slot allocation scheme for throughput enhancement in a millimeter-wave multi-Gbps WPAN system

This paper proposes a virtual time-slot allocation (VTSA) scheme for throughput enhancement to realize a multi-Gbps time division multiple access (TDMA) wireless personal area network (WPAN) system in a realistic millimeter-wave residential multipath environment. TDMA system without time-slot-reuse mechanism conventionally allocates one TDMA time-slot to only one communication link at a time. In the proposed VTSA scheme, taking advantage on the large path loss in the millimeterwave band, a single TDMA time-slot can be reallocated and reused by multiple communication links simultaneously (hence the name virtual), thus significantly increasing system throughput. On the other hand, allowing multiple communication links to occupy the same time-slot causes the generation of co-channel interference (CCI). The cross layer VTSA scheme is therefore designed to be able to maximize the throughput improvement by adaptively scheduling the sharing of time-slots, and at the same time monitor the potential performance degradation due to CCI. As a result, it is found that the VTSA scheme is capable of improving system throughput as much as 30% in both AWGN and multipath channels (line-of-sight (LOS) and non-line-of-sight (NLOS) environment). Additionally, by coupling with higher-order modulation schemes, the system is able to achieve up to a maximum throughput of 3.8 Gbps. It is also observed that higher-order modulations although have higher maximum achievable throughput in low CCI environment, the tolerance against increasing CCI is considerably lower than that of the lower-order modulations.

Beam switching support to resolve link-blockage problem in 60 GHz WPANs

In this paper, we propose a solution to resolve link blockage problem in 60 GHz WPANs. Line-of-Sight (LOS) link is easily blocked by a moving person, which is concerned as one of the severe problems in 60 GHz systems. Beamforming is a feasible technique to resolve link blockage by switching the beam path from LOS link to a Non-LOS (NLOS) link. We propose and evaluate two kinds of Beam Switching (BS) mechanisms: instant decision based BS and environment learning based BS. We examine these mechanisms in a typical indoor WPAN scenario. Extensive simulations have been carried out, and our results reveal that combining angle-of-arrival with the received signal to noise ratio could make better decision for beam switching. Our work provides valuable observations for beam switching during point-to-point communication using 60 GHz radio.

Beamforming Codebook Design and Performance Evaluation for 60GHz Wideband WPANs

The paper proposes a codebook design to support beamforming mechanism in a wide band millimeter-wave 60GHz wireless personal area networks (60GHz WPANs) in a realistic millimeter-wave environment. The codebooks are designed sym- metrically in order to mitigate the possible beam shift due to the large differences of wave lengthes at different sub-bands of a wide band communication system. In order to provide a high data rate and high performance with minimum power consumption in 60GHz systems, the codebooks are generated with 90 degree phase resolution without amplitude adjustment. The codebooks are designed for different numbers of antenna elements, supporting a multitude of antenna configurations. The paper provides codebook design mechanism, some example codebooks and some analysis on antenna gain loss due to phase shift errors of phase shifters. Simulation results shows that: (1) To keep the gain loss at the intersections of any two patterns inside the codebook lower than 1dB, the number of patterns inside the codebook shall be at least 2 times of the number of antenna elements used for pattern generation; (2) The designed codebooks are robust to phase shift errors: the gain loss is lower than 1dB with only 10% outage probability when standard deviation of phase shift errors at phase shifters is 0.5 (28.6 degree). The proposed codebooks are a feasible design, they are the key basis of the beamforming protocol in 60GHz WPANs (IEEE 802.15.3c).

Cognitive communication in TV white spaces: An overview of regulations, standards, and technology [Accepted From Open Call]

This article presents the latest developments in regulatory status and standardization initiatives in the field of TV white space cognitive communication systems. Updates on recent movements of regulatory bodies such as the U.S. FCC, U.K. OFCOM, European CEPT, Japanese MIC, and Singapore IDA in TV white space communications are first presented. The response of the industrial community toward these new regulations is then discussed, focusing on the activities in the IEEE 802 standards association. The latest developments of IEEE 802.11, 802.22, 802.15, 802.19, and DySPAN SC are described. Considerations on system design including PHY/MAC layer design in these standards are then listed and discussed. Lastly, potential usage models of cognitive communications in TV white spaces are presented, with emphasis on required parameters as guiding references to corresponding system design.

Enabling coexistence of multiple cognitive networks in TV white space

We address the problem of coexistence among wireless networks in TV white space. We present a standard independent framework to enable exchange of information relevant for coexistence based on two mechanisms: centralized and distributed. Both mechanisms introduce the use of multiradio cluster-head equipment (CHE) as a physical entity that acquires relevant information, identifies coexistence opportunities, and implements autonomous coexistence decisions. The major conceptual difference between them lies in the fact that the centralized mechanism utilizes coexistence database(s) as a repository for coexistence related information, where CHEs need to access before making coexistence decisions. On the other hand, the distributed mechanism utilizes a broadcast channel to distribute beacons and directly convey coexistence information between CHEs. Furthermore, we give a concise overview of the current activities in international standardization bodies toward the realization of communications in TVWS along with measures taken to provide coexistence between secondary cognitive networks.

Overview of TV White Spaces: Current regulations, standards and coexistence between secondary users

TV White Spaces (TVWS) refer to segments of the TV spectrum not used by licensed users in a given location. In recent years, regulation agencies throughout the world consider the possibility to open TVWS to unlicensed use, which is followed by standardization activities to realize it. One of the important aspects of unlicensed operation in TVWS is coexistence between heterogenous networks. This paper provides an overview of current regulations, standardization activities related to TVWS, while the main focus is IEEE P802.19.1 standardization project to enable coexistence in TVWS.

Beam Codebook Based Beamforming Protocol for Multi-Gbps Millimeter-Wave WPAN Systems

In this paper, we propose a feasible beamforming (BF) scheme realized in media access control (MAC) layer following the guidelines of the IEEE 802.15.3c criteria for millimeter-wave 60GHz wireless personal area networks (60GHz WPANs). The proposed BF targets to minimize the BF set-up time and mitigates the high path loss of 60GHz WPAN systems. It is based on designed multi-resolution codebooks, which generate three kinds of patterns of different half power beam widths (HPBWs): quasi-omni pattern, sector and beam. These three kinds of patterns are employed in the three stages of the BF protocol, namely device-to-device (DEV-to-DEV) linking, sector-level searching and beam-level searching. All the three stages can be completed within one superframe, which minimizes the potential interference to other systems during BF set-up period. In this paper, we show some example codebooks and provide the details of BF procedure. Simulation results show that the setup time of the proposed BF protocol is as small as 2% when compared to the exhaustive searching protocol. The proposed BF is a complete design, it re-uses commands specified in IEEE 802.15.3c, completely compliant to the standard; It has thus been adopted by IEEE 802.15.3c as an optional functionality to realize Giga-bit-per-second (Gbps) communication in WPAN Systems.